<nb-card>
  <nb-card-header>Button Sizes</nb-card-header>
  <nb-card-body>
    <button nbButton size="xsmall">x-small</button>
    <button nbButton size="small">small</button>
    <button nbButton size="medium">medium</button>
    <button nbButton size="large">large</button>
  </nb-card-body>
</nb-card>
